The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
In data links, the transmission path used for transmitting signals is known to cause interference in telecommunication. Another main cause for errors in communication is thermal noise. In order to diminish the effects of thermal noise and interference caused by the transmission path, efficient transmission methods are required.
In many systems, coherent detection is utilized in receivers. In coherent detection, the carrier phase of the received signal must be detected at the receiver. In non-coherent detection, phase information is not required. However, due to better performance, coherent detection is widely used although the receiver complexity is greater. It is common to add a reference signal to a payload signal so that the signal may be received coherently at a receiver. In some moderns systems, constant amplitude zero autocorrelation waveform (CAZAC) sequences are used as reference signals. Cyclic shift versions of a CAZAC sequence have high orthogonality with each other. Thus, cyclic shifted versions of such a sequence may be used as a reference signal. Also other sequences may be used, such as computer searched Zero-Autocorrelation (ZAC) sequences.